Variable aperture for electron microscope



p 9, 1958 v IKAZUYHIKO AKASHI ETAL 2,851,610

VARIABLE APERTURE FOR ELECTRON MICROSCOPE Filed Sept. 8, 1954 v 2Sheets-Sheet 1 FIGS FIG4' p 1958 KAZUHIKO: AKASHI ET AL 2,851,610

VARIABLE APERTURE FOR ELECTRON MICROSCOPE Filed Sept. 8, 1954 2Sheets-Sheet 2 771 rim 0mm mow)? United States Patent VARIABLE APERTUREFOR ELECTRON MICROSCOPE Kazuhiko Akashi, Tokyo, and Tatsunosuke Masuda,Yokohama, Japan Application September 8, 1954, Serial No. 454,734

8 Claims. (Cl. 250-495) This invention relates to an improvement inelectron mlcroscope' structures and more particularly to theconstruction of the variable aperture thereof.

An object of this invention is to provide means conducive to anefficacious electron microscope structure which makes it possible thatthe magnitude of the aperture thereof be varied simply and.continuously.

Generally the construction of the variable aperture to be used for anelectron microscope has hitherto been complicated and moreover unhandy.According to one aspect of this invention, however, the variableaperture comprises a lateral shaft rotatably and slidably mounted in aneccentric sheave, which is in turn rotatably supported by the microscopetube. Two diaphragms are arranged in a spaced relation from each otherabout the axis of said shaft and fixed to the end of said shaft, saiddiaphragms projecting into the bore of said tube. One of said diaphragmsmay be made in a rectangular form having a beveled inner edge, while theother diaphragms may be provided with a triangular recess, the edges ofwhich are also beveled. Sealing means are arranged between said shaftand sheave as well as between said sheave and tube.

Various further and more specific objects, features and advantages ofthe invention will appear from the description given below taken inconnection with the accompanying drawings illustrating by way of examplecertain preferred forms of the invention.

In the drawings:

Fig. 1 shows a sectional elevation representing a constructional exampleof this invention.

Fig. 2 shows a locating device.

Fig. 3 shows a perspective view of diaphragms with one shaft.

Fig. 4 shows a perspective view of diaphragms with two shafts.

Fig. 5 shows a perspective view of diaphragms of another form.

Referring now to Figs. 1 and 2 further in detail, a lateral shaft 0 isrotatably and axially slidably mounted through an eccentric sheave d,which is in turn rotatably supported by the microscope tube. Twodiaphragms a and b are fixed to the end of said shaft 0 projecting intothe bore of said microscope tube in such a way that these diaphragms aredisposed in spaced relation with respect to each other about the axis ofsaid shaft 0.

One of said diaphragms, for instance the upper one denoted by a in Fig.1, is made in a rectangular form having a beveled inner straight edge,while the other diaphragm, for instance lower one denoted by b in Fig.1, is provided with a triangular recess, the edges of which are alsobeveled. Although, in these figures, each of the diaphragms is showndiagrammatically as a plate, the diaphragm 'b, which is provided withthe triangular recess, is preferably made of two pieces, so joined as todefine the sides of said recess therebetween. This arrangement ensuresan easy access to the apex of sald 2,851,610 Patented Sept. 9, 1958 2recess and thus enables thorough cleaning of the side edges of saidpieces to be effected.

Upon rotation of the shaft 0, the two diaphragms a and b approach ormove away from each other, as the case may be, when viewed from above.The area through which the electron beams pass can thus be varied frommaximum to nil without abrupt change, as will be clear from B and C ofFig. 2. The position of the aperture can be controlled by shifting theshaft 0 axially. When the eccentric sheave d is turned, the aperturewill move to the left or right in a direction transverse to the axis ofsaid shaft 0 when viewed from above. As shown in Fig. l, sealing meansare provided between said lateral shaft 0 and eccentric sheave d as wellas between said sheave and microscope tube, whereby the ambient air iseffectively prevented from entering into the evacuated bore of themicroscope.

A modified embodiment of diaphragms fixed to one lateral shaft is shownin Fig. 3. In this embodiment, both diaphragms are provided withtriangular recesses. The form of the aperture is thus rectangularinstead of triangular as in the preceding example.

In a further modified embodiment of the invention, as shown in Fig. 4,two sets of aperture control devices substantially like those describedin connection with Figs. 1 and 2 are employed. These devices includediaphragms a and b arranged on separate shafts c oriented at rightangles to each other. None of the diaphragms is, however, in this caseprovided with a triangular recess. The form of the aperture is,therefore, rectangular.

Still a further modification of the aperture control device is shown inFig. 5. The lateral shafts c and c are arranged in a parallel andstaggered relation with respect to each other and at different levels.Although not shown, each of these shafts is rotatably and slidablymounted in an eccentric sheave, which is in turn rotatably supported bythe microscope tube, as in the case of the first described embodiment ofthe invention. Diaphragms a and b are fixed to the end portions of saidlateral shafts projecting into the bore of said tube. Each diaphragm isprovided with a triangular recess with beveled side edges. The size ofthe aperture can be varied by the rotation of the lateral shafts, andthe location of the aperture can be adjusted by the axial movement ofthese shafts and/ or by the rotational movement of the eccentric sheaves(not shown).

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

1. In an electron microscope having a hollow microscope tube defining apath of movement for electron beams; a control arrangement forregulating the crosssection of said path and comprising shaft meansextending into the interior of said tube substantially transversely tosaid path and arranged for rotation and for reciprocal axialdisplacement relative to said tube and substantially transversely ofsaid path, diaphragm means carried by said shaft means within said tubeand rotatable and displaceable with said shaft means, said diaphragmmeans being shaped and constructed to define an aperture through whichsaid electron beams pass during their movement along said path, andoperable means connected to said shaft means for displacing the latterin a direction substantially transverse to the direction of said axialdisplacement, whereby the position of said aperture relative to saidpath is determined through said substantially transverse displacementsof said shaft means together with said diaphragm means, respectively,while the effective cross-sectional shape and area of said aperture aredetermined through the extent of rotation of said shaft means togetherwith said. diaphragm means.

2. In a microscope according to claim 1, said shaft means comprising asingle shaft having a longitudinal axis, said diaphragm means comprisingfirst and second diaphragms connected to said shaft at one end thereofand disposed in respectiveplanes on opposite sides of said axis, saiddiaphragms being provided with respective inner edges facing each other,said inner edge of saidfirst diaphragm being straight, and said inneredge of said second diaphragm being provided with an angular recess,whereby a triangular aperture is defined by said diaphragms.

3. In a microscope according to claim 2, said planes in which saiddiaphragms are disposed being parallel to one another and to said axis,said inner edge of said first diaphragm being parallel to said axis.

4. In a microscope according to claim 3, said inner edges of saiddiaphragms being beveled.

5. In a microscope according to claim 1, said shaft means comprising asingle shaft having a longitudinal axis, said diaphragm means comprisingfirst and second diaphragms connected to said shaft at one end thereofand disposed in respective planes on opposite sides of said axis, saiddiaphragms being provided with respective inner edges facing each other,said inner edge of said first diaphragm being provided with a firstangular recess, said inner edge of said second diaphragm being providedwith a second angular recess, said recesses being aligned with oneanother, whereby a quadrangular aperture is defined by said diaphragms.

6. In a microscope according to claim 1, said shaft means comprising twoshafts each having a longitudinal axis, said diaphragm means comprisingat least two diaphragms connected, respectively, to said shafts atcorresponding adjacent portions of the latter, said operable meanscomprising a pair of eccentric sheaves rotatably arranged on said tubeand supporting said shafts, respectively, whereby said shafts may bedisplaced independently of one another and transversely of theirrespective axes through rotation of said sheaves.

7. In a microscope according to claim 6, said axes of said shafts beingparallel to one another and spaced from one another in the direction ofsaid path, said diaphragms having respective outer edges connected,respectively, to said shafts, and further having respective inner edgesfacing one another and provided, respectively, with angular alignedrecesses, whereby said diaphragms define a quadrangular aperture.

8. In a microscope according to claim 6, said axes of said shafts beingsubstantially perpendicular to one another, said diaphragm meanscomprising two first diaphragms connected to one of said shafts anddisposed a predetermined distance from one another in respective firstplanes on opposite sides of said axis of said one shaft, said firstdiaphragms being provided with respective straight inner edges facingone another, and two second diaphragms connected to the other shaft anddisposed in respective second planes on opposite sides of said axis ofsaid other shaft, said second diaphragms being provided with respectivestraight inner edges facing one another and being oriented substantiallyat right angles to said inner edges of said first diaphragms, thedistance between said second diaphragms being less than the distancebetwen said first diaphragms, and said second diaphragms being locatedbetween said first diaphragms, whereby a quadrangular aperture isdefined by said first and second diaphragms.

References Cited in the file of this patent FOREIGN PATENTS

